When it comes time to measure your Maxim-X valve clearances and to replace shims, there are purists who will tell you never to use resized / remachined shims. In the case of the air-cooled XJs which have a shim-over-bucket design, I might be inclined to agree. But, in the case of the liquid-cooled Maxim-X with its shim-under-bucket design, there's no need for concern.

Shim-Over-Bucket		Shim-Under-Bucket

Shim-OVER-bucket systems have the shim in direct contact with the cam lobe so an argument could be made that having the surface remachined could result in imperfections that might wear on the cam in the long run or might even encourage spitting shims out because of the lateral friction between the two parts. But the Maxim-X's shim-UNDER-bucket design means the shims don't contact the cams. In fact, the shims don't experience any appreciable frictional component at all. They simply sit atop the valves and act as a spacer, in simple compression, between the valves and buckets. Unless someone wants to argue that remachining a shim will change its molecular properties and compression resistance (not gonna happen), there's really no basis for concern. A remachined / resized Maxim-X shim is identical in operation in every way to a factory shim of the same size.

Measure your factory shims!

There are actually reasons why someone might prefer a resized shim over a shim straight from Yamaha. I've been hosting the Maxim-X shim pool for several years now and in that time I've seen some crazy sh*t where factory shims are concerned.

• I've seen factory shims without any size markings at all.
• I've seen factory shims with two entirely different size stamps on them (ex. 160 on one side and 195 on the other)
• It's pretty common to find shims marked 0.02mm off of the actual size
• I've seen shims which have a size stamped on them that's much larger than the actual size (ex. 230 on a 190)
• I've seen shims which have a size stamped on them that's much smaller than the actual size (ex. 160 on a 195)

For the most part, factory shims come marked properly but that leads to assumptions about ALL shim markings being correct and you know what they say about assumptions - if you assume, you make an ass outta u and outta me. It can certainly happen when people blindly rely on the factory marked sizes just because they look so "official". Unfortunately, doing so just might result in a valve colliding with a piston! But when shims are remachined to take material off and make them thinner, they always need to be measured afterward just so I can file them away properly - all the same sizes together etc.... So the factory markings are removed and a new size written on them. But even if they were left blank (which will happen even when rewritten - the ink is not very resilient) it would still be an improvement because X owners would be forced to measure the resized shims themselves and thus they can be certain of the resulting size.